Add a tox environment for flexible candidate checking

By default ci_check_all_candidate_files.py, does as it implies and
checks all candidates for the current election.

Add new operation modes for:
 1. Checking all files for the current git commit '--HEAD'
 2. Checking all files specified on the command line

We also add a voting job on the check pipeline only for validating
the current review.  Local users are encouraged to use this as:

 tox -e ci-checks-review ; or
 tox -e ci-checks-review -- path/to/file

Change-Id: I0c82c59409bb58169840de42c02072aeae182b2b
Co-authored-by: Doug Hellmann <doug@doughellmann.com>

.zuul.d/jobs.yaml

@@ -1,10 +1,21 @@
 - job:
-    name: election-tox-ci-checks
+    name: election-tox-ci-checks-election
     parent: openstack-tox
     description: |
-      Run the ci-checks tox environment
+      Run the ci-checks-election tox environment
 
       This environment runs the easy, for a machine, to validate election
       checks.
     vars:
-      tox_envlist: ci-checks
+      tox_envlist: ci-checks-election
+
+- job:
+    name: election-tox-ci-checks-review
+    parent: openstack-tox
+    description: |
+      Run the ci-checks-review tox environment
+
+      This environment runs the easy, for a machine, to validate election
+      checks against only files modified in the current review.
+    vars:
+      tox_envlist: ci-checks-review

.zuul.d/project.yaml

@@ -7,12 +7,13 @@
       jobs:
         - openstack-tox-py27
         - openstack-tox-linters
-        - election-tox-ci-checks
+        - election-tox-ci-checks-review
+        - election-tox-ci-checks-election
     gate:
       jobs:
         - openstack-tox-py27
         - openstack-tox-linters
-        - election-tox-ci-checks
+        - election-tox-ci-checks-election
     post:
       jobs:
         - publish-tox-docs-static

openstack_election/cmds/ci_check_all_candidate_files.py

@@ -16,6 +16,7 @@ from __future__ import unicode_literals
 
 import argparse
 import os
+import subprocess
 
 from openstack_election import check_candidacy
 from openstack_election import utils
@@ -75,6 +76,19 @@ def check_for_changes(projects, filepath, limit):
     return bool(changes_found)
 
 
+def find_modified_candidate_files():
+    "Return a list of files modified by the most recent commit."
+    results = subprocess.check_output(
+        ['git', 'diff', '--name-only', '--pretty=format:', 'HEAD^']
+    ).decode('utf-8')
+    filenames = [
+        l.strip()
+        for l in results.splitlines()
+        if l.startswith(utils.CANDIDATE_PATH + '/')
+    ]
+    return filenames
+
+
 def main():
     description = ('Check all files under the current open election are valid')
     parser = argparse.ArgumentParser(description)
@@ -90,6 +104,14 @@ def main():
                         default=utils.conf['release'],
                         help=('The relase to validate candidates against.  '
                               'Default: %(default)s'))
+    parser.add_argument('--HEAD',
+                        dest='head_only',
+                        action='store_true',
+                        default=False,
+                        help='Validate all candidates.')
+    parser.add_argument('files',
+                        nargs='*',
+                        help='Candidate files to validate.')
 
     args = parser.parse_args()
     errors = False
@@ -99,7 +121,14 @@ def main():
 
     projects = utils.get_projects(tag=args.tag, fallback_to_master=True)
 
-    for filepath in utils.find_candidate_files(election=args.release):
+    if args.files:
+        to_process = args.files
+    elif args.head_only:
+        to_process = find_modified_candidate_files()
+    else:
+        to_process = utils.find_candidate_files(election=args.release)
+
+    for filepath in to_process:
         candidate_ok = True
 
         candidate_ok &= validate_filename(filepath)

tox.ini

@@ -29,7 +29,10 @@ commands = {posargs}
 [testenv:docs]
 commands = sphinx-build -v -W -b html -d doc/build/doctrees doc/source doc/build/html
 
-[testenv:ci-checks]
+[testenv:ci-checks-review]
+commands = ci-check-all-candidate-files {posargs:--HEAD}
+
+[testenv:ci-checks-election]
 commands = ci-check-all-candidate-files
 
 [flake8]